OAuthException not catched with C# FacebookSDK

I try to get my code working with catching certain errors. I store the 开发者_Python百科token for a user after he or she grants permission to my app (this is a WP7 app). When I try to post on the wall by using the stored token it works. When I remove the permissions on facebook it throws an OAuthException. I can't catch it it seems. My app just crashes. This is the code I used:

    private object PostToFacebook()
    {
        _fbApp = new FacebookClient(_appsettings.faceBookToken);

        FacebookAsyncCallback callback = new FacebookAsyncCallback(this.postResult);

        var parameters = new Dictionary<string, object>();
        parameters.Add("message", "message on wall");
        try
        {
            _fbApp.PostAsync("me/feed", parameters, callback);
        }
        catch (Exception ex)
        {

        }
        return null;
    }

    private void postResult(FacebookAsyncResult asyncResult)
    {
        if (asyncResult.Error == null)
        {
            status = "succes";
        }
        else
        {
            status = "error" + asyncResult.Error.Message;
        }
    }

The try catch doesn't catch anything and the generic exception handler in my app.xaml.cs either.

Any ideas how to catch this error so I can ask the user to authenticate again?

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Put your try..catch in the callback.

You can also catch exceptions globally by handling the UnhandledException event on the App object.